1) Field of the Invention
The invention generally relates to the field of hydraulically actuated valve lifters for internal combustion (xe2x80x9cI.C.xe2x80x9d) engines. More particularly, the invention relates to an improved valve lifter body and internal lifter apparatus configuration which restricts particulate contaminants contained in the oil from entering the lifter internal mechanism and fouling lifter operation.
2) Description of the Related Art
In the I.C. engine field, there exists a continuing pursuit of reliability in engine operation. An ongoing problem related to reliability is engine component failures related to lubrication interruptions and blockages. In the field of valve lifters, which actuate valves either directly or through related valve train components, a constant supply of fresh filtered oil is necessary for reliable long-term operation. As shown in FIG. 1, pressurized oil from the I.C. engine oil pump is supplied via oil passages (galleries) 1 which communicate with the circumferential groove around the outside of the lifter assembly 2. The oil enters the lifter body via oil ports 3 located on the side of the lifter assembly 2. Oil enters the hollow plunger through one or more oil inlet holes 4 to the plunger cavity to form an oil column.
The lifter consists of a xe2x80x9cplungerxe2x80x9d closely fitted into, but freely slideable, within a xe2x80x9cbodyxe2x80x9d with a lower chamber left between the plunger and body. The bottom of the plunger is fitted with a check valve that allows free flow downward into the lower chamber but prevents reverse flow upward out of it.
During engine operation the cam lobe rotates and forces the lifter upward against the opposing force of the valve spring to open the engine valve. During the valve opening event, a controlled leakage between the plunger and body corresponds to a downward plunger movement that gives the hydraulic lifter its automatic adjustment ability. At the completion of the valve closing event, the valve returns to the fully closed position, the lifter is again on the base circle of the cam and a small amount of lash has therefore accumulated in the valve train.
At this point upon completing a valve lift event, the lifter spring, assisted somewhat by engine oil pressure, pushes the plunger upward to remove all accumulated lash from the valve train. As the plunger moves upward sufficient oil is sucked down through the ball check valve 5 to solidly fill the lower chamber. As the engine continues to rotate, the cam lobe again forces the lifter upwards to open the engine valve and oil in the lower chamber is sealed by action of the check ball which closes almost instantly.
To operate properly, the lifter must receive adequate amounts of clean oil, otherwise free movement of the plunger or the ball check valve seating/sealing will be affected. Dirt/debris particulate matter will cause improper operation of the lifter resulting in valve train noise or ultimately lead to permanent engine failure. In the case where the particulate debris has gained access to the lifter interior cavity, the particulates can impair operation of the lifter check valve 5 located therein by interposing between the ball and valve seat 6. If this condition were to occur, the ball fails to seat thereby allowing oil to flow back from the lower chamber to the plunger chamber. Additional failure can occur with debris becoming lodged between the plunger and body thereby restricting free movement. These failures result in loss of hydraulic function with resultant valve train noise and customer dissatisfaction. These types of failure account for 3-5% of all valve train related warranty returns.
Particulates contained in the oil of an I.C. engine have several sources. One source is from debris contained within the engine from machining and manufacture and/or repair. Another is from accumulations resulting from engine operation. These sources are routinely dealt with through oil filtration; however, oil is sometimes supplied throughout the engine during start up without filtration because the engine oil filter is in a full load bypass mode. As a result, particulates are passed throughout the engine including the valve lifters. Mesh filtration systems to address this problem would lead to clogging and an unserviceable oil blockage condition.
This invention is directed to a mechanical oil filtration and redirecting system to control the access and passage of particulates in and through the valve lifter. The object of the invention system is to filter (limit access) large particulates and to redirect or deflect the smaller particulates which do access the lifter to-pre-determined locations where little or no operational impairment can occur.
The invention is a valve lifter incorporating exteriorly and interiorly located structure that limits initial particulate access to the lifter, and re-directs particulates in the oil which do pass through to the valve lifter so as to prevent operational impairment of the lifter caused by the particulates.
Access of particulates to the lifter is initially limited by a controlled gap located between the lifter body and the lifter bore in the surrounding I.C. engine. Following this controlled gap, a second controlled gap exists inside the lifter between the inside of the lifter valve body and the lifter plunger. Once the oil is passed through the first two controlled gap limitations, the oil, at this point containing only smaller particulates, is deflected by an insert located within the lifter internal cavity upwardly towards the push rod seat (valve train actuation portion of the lifter) and oil metering valve. The mechanically filtered oil is then directed towards the oil supply hole located in the upper portion of the deflector and thereafter into the low pressure side of the plunger cavity which includes, at its lower end, the lifter check valve.
In addition to providing the final structural elements for mechanical oil filtration, the oil-deflecting insert also traps the oil within the lifter above the height of the plunger oil feed hole. This containment of the oil results in a retained oil column within the lifter cavity having greater height and therefor less oil fill requirement at engine start up to initiate proper lifter operation.